1. Field
Example embodiments relate to nonvolatile memory devices and methods of fabricating the same. Other example embodiments relate to charge-trap nonvolatile memory devices and methods of fabricating the same.
2. Description of the Related Art
Nonvolatile memory devices may be used in various data communication devices, e.g., digital cameras, mobile phones, personal digital assistants (PDAs) and/or MPEG-3 (MP3) players because of their ability to maintain data stored therein even when power is not supplied.
Nonvolatile memory devices may be classified into floating-gate memory devices and charge-trap memory devices. A charge-trap memory device may include a charge-trap structure which has, for example, a tunnel layer, a charge-trap layer, and a blocking layer. A gate electrode may be disposed on a charge-trap structure, and spacers may be disposed on the sidewalls of the gate electrode.
At least part of a charge-trap structure may be patterned using a gate electrode or spacers as etching masks. However, when patterning a charge-trap structure using a gate electrode as an etching mask, the sidewalls of a blocking layer may create an undesirable flow of charge from the gate electrode to a charge-trap layer, thereby causing the breakdown voltage of the transistor to deteriorate. When patterning a charge-trap structure using spacers as etching masks, a charge-trap layer may protrude beyond the sidewalls of a gate electrode by as much as the thickness of the spacers. Charge may be injected into the charge-trap layer by the influence of the vertical electric field generated by the gate electrode. Then, the charge injected into the charge-trap layer may spread throughout the entire charge-trap layer. However, because charges in the portions of the charge-trap layer that protrude beyond the sidewalls of the gate electrode are not directly affected by the vertical electric-field of the gate electrode, charges may not be erased during an erase operation and remain in the portions of the charge-trap layer that protrude beyond the sidewalls of the gate electrode even after the erase operation. The charges remaining in the portions of the charge-trap layer that protrude beyond the sidewalls of the gate electrode may adversely affect the threshold voltage of a transistor and cause the characteristics of the entire nonvolatile memory device to deteriorate.